As of 2012, approximately 22 million Americans required treatment for drug dependence. Drug addiction arises as a consequence of changes in brain circuitry induced by drug exposure and resultant dopamine release. Synaptic plasticity processes underlie numerous aspects of drug abuse and addiction, including the formation of drug-clue, action-outcome, and stimulus-response associations affecting instrumental behavior, as well as extinction of drug-seeking behavior. Synaptic plasticity is heavily dependent on the expression and function of immediate early genes (IEGs), in particular activity-regulated, cytoskeletal-associated (Arc) and early growth response-1 (egr1/zif268) genes. These genes critically mediate consolidation and reconsolidation of long-term memories, including memories implicated in aspects of drug abuse and addiction. Understanding the regulation of these IEGs is therefore significant in its potential to identify novel therapeutic targets to disrupt aberrant plastic changes contributing to drug abuse and addiction. Many studies have focused on understanding processes mediating transcriptional regulation of IEGs, as well as on dendritic trafficking and local translation of Arc mRNA. However, to date there are no studies in the extant literature examining the basic cellular process of nuclear export of mRNAs in general, much less IEG RNAs in particular, in the adult mammalian brain. Our experimental evidence suggests that nucleocytoplasmic export of these IEG mRNAs differs in striatonigral (direct pathway) vs. striatopallidal (indirect pathway) neurons in dorsal striatum. Further, our recent data suggest that the nuclear export of IEG mRNAs in striatonigral efferent neurons may be regulated by dopamine. The overall goal of the proposed studies is thus to test the novel hypothesis that there are differences in nucleocytoplasmic export of IEG mRNAs in striatal efferent neuron subpopulations. In Specific Aim 1, we will determine the phenotypic distribution of known mediators of nucleocytoplasmic mRNA export and their co-localization with IEG mRNAs in striatal efferent neuron subpopulations. In Specific Aim 2, we will differential centrifugation and FACS to separate nuclei from striatonigral and striatopallidal neurons, followed by ribonucleoprotein immunoprecipitation and RT-PCR to biochemically assess the interaction of Arc and zif268 with specific ribonucleoprotein complexes involved in nuclear export. In Specific Aim 3, we will determine the role of dopamine D1 receptor activation in the regulation of nuclear export of IEGs in striatonigral efferent neurons. Given the lack of data regarding the regulation of nuclear export of mRNAs in neurons of the adult mammalian brain and potential regulation of this process by neurotransmitter systems, including DA, successful completion of the proposed studies will provide seminal insight into the regulation of these critical plasticity-related IEGs n striatal circuitry intricately involved in drug abuse and addiction. These findings thus have the potential to reveal novel therapeutic targets to modulate striatal plasticity so as to improve treatment outcomes in individuals with histories of drug abuse and addiction.